Geochemical Fractionation of Lanthanides in Stream Sediments around Bwanebwa Area, Pan African Fold Belt Cameroon

Fifteen stream sediment samples were collected in Bwanebwa area, situated southwestern part in the central domain of the Pan African Fold Belt in Cameroon. Samples were analyzed by Aqua Regia Inductive Coupled Plasma Mass Spectrometry analytical technique. The chemical analyses revealed a wide variability of lanthanide concentrations REE = 1471.56 7674.2 ppm displaying a normal distribution pattern. Lanthanides show a high enrichment in La, Ce, Pr, Nd, and the proportion enrichment of REEs is still similar with increasing atomic number. The order of the average concentrations of REEs is Ce La Nd Pr Sm Gd Dy Er Tb Ho Yb Eu Tm Lu, which was different to that found in the Oddo Harkins rule, earth’s crust, upper continental crust, South China Sea, mean REE values in oceanic crust, Redang Island Marine Sediment in Terengganu Coastal Waters, Bayan Obo ores, Edéa, suggesting that REEs set up a complex group. The LREE HREE ratio 31.57 35.24, av. = 32.82 showed that the content of LREE 1425 7449.8, av. = 3699 is significantly higher than that of HREE 46.56 224.4, av. = 112.07 . LREEs account for 97.06 of the total REEs and this percentage is in agreement with the trend that was observed in the earth’s crust and in the Bayan Obo ores. Chondrite normalized REE distribution patterns are identical, indicating the consistency of geochemical distribution of REEs in stream sediments. They are strongly fractionated, with LREEs significantly fractionated LaN YbN = 11.74 27.93, av. = 21.04 relative to HREEs GdN YbN = 7.40 16.69, av. = 13.35 , implying that HREEs are more soluble and more complex than middle or LREE and are more strongly absorbed on most substrates. Positive Ce anomaly Ce Ce = 1.04 1.07 and negative Eu anomaly Eu Eu = 0.097 0.17 were observed, indicating that di erentiation occurred between Ce, Eu and other lanthanides. Therefore the positive Ce anomaly recorded represents an enrichment of Ce compared with its neighboring elements. A five factor model of the REEs that accounts for 1.998 of the total data cumulative variance have been observed, with the communality values 0,996 1 reflecting stronger community structure. Principal component analysis results in five components that explain 100 of the total variance, with the placement of elements in three major principal components, in which elements scattering in the rotated space displaying their mutual association. The results provide evidence for similar input sources and common geochemical characteristics of REEs. Lanthanide concentrations in Bwanebwa area were of geogenic origins and not influenced by anthropogenic sources. The abundance of REEs is related to the lithology made up of granites and associated pegmatites. Cerium shows the highest average content of REEs, followed by La, Nd, Pr, Gd, Sm, hence pattern of Ce distribution shows higher than the other lanthanides. LREEs La, Ce, Pr, Nd and Ga fall above the upper background threshold limit and are considered as anomalous. Therefore the results of this work serve as guide for lanthanides exploration in Bwanebwa area. Ndema Mbongué Jean-Lavenir "Geochemical Fractionation of Lanthanides in Stream Sediments around Bwanebwa Area, Pan-African Fold Belt (Cameroon)" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-3 , April 2020, URL: https://www.ijtsrd.com/papers/ijtsrd30430.pdf